The goal of this project is to gain a scientific understanding of the origins and the mechanisms of human tactile sense. In particular, the major focus is on how the shape, softness and surface texture of objects indented, stroked or vibrated on the primate fingertip skin are encoded by populations of mechanoreceptors. For these stimuli, a quantitative understanding of what spatio-temporal loads are imposed on the skin, how they are transmitted through the skin, and which mechanical signals are transduced by each type of spatially distributed mechanoreceptor populations is to be developed. The major components and of the proposed study are (1) biomechanical data gathered using a novel acoustic imaging system and a high precision tactile stimulator that have been developed over the past year, (2) unique 2- and 3- dimensional computational models of the primate fingertip, and (3) application of linear and nonlinear system identification techniques to help develop a theory of tactile coding. The specific aims of this proposal are (1) to obtain high resolution anatomical and strain images of the primate fingerpad skin using Ultrasound Backscatter Microscopy (UBM), (2) to obtain dynamic fingerpad impedance data using the Tactile Stimulator, (3) to use the data from experiments to improve high resolution computational models of the fingerpad and perform finite element simulations involving contact with soft, textured and concave rigid objects under varying dynamic conditions, and (4) to use the results from both experiments and computer simulations to develop a systems theory of tactile coding. At each stage of the project, the experimental data, computational model simulations, and the theory will aid one another. The benefits of this research include the separation of the role of tissue mechanics from receptor dynamics in peripheral neural response, as well as eventually aiding the separation of the roles of peripheral and central mechanisms in somatosensory information processing. One example of a long term benefit from a clinical standpoint will be the ability to design better tests for the evaluation of tactile sensibility of normal and impaired hands to aid diagnosis, treatment, and rehabilitation.